Preparation of unsaturated hydroperoxides from N-alkenyl-N′-p-tosylhydrazines

Abstract

Gordon Street, London WCI H OAJ U maturated hydroperoxides ( R' R2CH 0,H ), 2-phenylpent-4-enyl hydro peroxide (1 ), 3-phenyl hex-5en -2-yl hydroperoxide ( Z ) , 5-methyl hex-5-en -2-yl hydroperoxide (3), cyclo-oct -4-enyl hydroperoxide (1 8), and cyclo-oct-3-enyl hydroperoxide (24) have each been prepared from the corresponding carbonyl compound ( R1R2CO) by the sequence: i, conversion to thep-tosylhydrazone ( R'R2C=N-NHTs); ii, reduction with sodium cyanoborohydride at pH 3.5 to give the N'-p-tosylhydrazine ( R1R2CH-N H-NHTs); and iii, oxidation with hydrogen peroxide and sodium peroxide. Isomerisation occurs in the preparation of the cyclo-octenyl hydroperoxides, particuarly if the pH falls markedly below 3.5 in the reduction step.Non-allylic alkenyl hydroperoxides are principal precursors of cyclic peroxides. Studies of the cyclisations, which occur under both radical and polar 3*5-8 conditions, contribute to an understanding of important processes such as lipid peroxidation and the oxidative degradation of rubber. The cyclic peroxides themselves serve as useful models for investigating the chemistry of naturally occurring substances such as prostaglandin endoperoxides. They also provide a convenient source of theoretically interesting diradicals, and have potential as intermediates in the stereocontrolled syntheses of polyoxygenated compounds. Certain &,&-unsaturated hydroperoxides are also precursors of gem-dialkylperoxonium ions which are a new, and as yet little studied, class of oxygen transfer rea g e n t ~. ~ With the single exception of 2-rnethylhex-5-en-2-yl hydroperoxide, which was prepared by silver(1)-assisted perhydrolysis of the corresponding bromide: all the non-allylic alkenyl hydroperoxides reported in the literature are primary or secondary and have been made by the perhydrolysis of alkenyl methanesulphonates under basic conditions. 1-8,10 We have found several examples where these reactions fail or afford hydroperoxides in only very poor yield. In an attempt to provide an alternative route to such hydroperoxides, we decided to investigate the use of the oxidation of N-alkenyl-N'-p-tosylhydrazines. The method is based on that applied by Caglioti and co-workers" to the preparation of a small number of saturated alkyl hydroperoxides (Scheme 1). This approach appears attractive in that high yields are reported for each of the three steps. However, the method has not found general use.

Asymmetric Catalysis by Vitamin B12. The Mechanism of the Cob(I)alamin‐Catalyzed Isomerization of 1,2‐Epoxycyclopentane to (R)‐Cyclopent‐2‐enol

“…The ESR at 100 K, however, shows signals explained by two coupling constants of 2.44 and 4.69 mT, corresponding to a locked conformation characterized by dihedral angles of 49 and 12.5" between the p orbital and the H-C bonds of the two neighbouring CH, groups [33]. From the ESR of the 2methoxycyclopentyl radical at 263 K, two coupling constants of 3.60 mT (H-C(5)) and 2.20 mT (H-C(2)) have been derived [34]. This can be explained by the fast oscillation of the CH, group described above and by a mean dihedral angle of 49"between the H-C(2) bond and the p orbital.…”

Peroxide synthesis from alkyl halides, alcohols and alkenes

“…Alkyl bromides, which are readily available intermediates, have been revitalized in peroxide synthesis by two reactions, one for hydroperoxides and the other for dialkyl peroxides. The peroxy mercuration-demercuration of alkenes has been reported for obtaining secondary alkyl peroxides bearing/3-functional substituents (14). Several mercury salts have been employed, namely Hg(OAc)2, Hg(NO3)2 and Hg(C104)2, all of which have limitations in reactions, yields, and scope.…”

Copper(I)-Catalyzed Intramolecular Addition of N-Chloroamines to Double Bonds under Aprotic Conditions. Towards a Stereoselective Catalytic Radical Reaction

“…To a solution of p-toluenesulfonyl chloride (57 g, 0.3 mol) in CH 2 Cl 2 (300 mL) were added pyridine (23.2 mL, 0.3 mol) and 2phenyl-4-pentenol 14 (40.6 g, 0.25 mol) at 0°C. The reaction was stirred overnight at r.t. and then poured into H 2 O (300 mL).…”